The coolant used in association with machine tools is relatively costly, and thus an attempt is made to reuse the coolant. During use, however, the coolant becomes highly contaminated with metal chips and the like which must be removed prior to reuse of the coolant.
Various techniques and apparatus have been utilized in an attempt to clean the coolant to permit reuse. One commonly used apparatus employs a vacuum or suction-type separator wherein the contaminated or dirty coolant is deposited into a tank having a cleated drag conveyor movable along a bottom wall thereof, which conveyor collects and removes from the tank the solid contaminants such as metal chips and the like which tend to settle onto the bottom wall. It is also conventional to provide a disposable filter media, such as a paper filter, which is fed along the bottom wall by the conveyor to assist in collecting and removing the contaminants. A pump disposed externally of the tank has an inlet suction pipe which communicates with the coolant in the vicinity of the bottom of the tank, whereby the pump sucks the cleaned coolant from the tank and then pressurizes the coolant so as to supply it to a discharge point for further reuse.
In the separator or filtration unit of the aforementioned type, as the drag conveyor and filter media move along the bottom wall of the main portion of the tank which contains a quantity of dirty coolant therein, the solids which settle to the bottom of the tank collect on the filter media to hence create a layer of sludge-like material which is movably advanced through the tank toward a discharge opening disposed at one end of the apparatus. However, the apparatus also includes a discharge section disposed between the main tank section and the discharge opening. This discharge section slopes upwardly from the tank section to the discharge opening so that the cleated conveyor and filter media are hence moved upwardly along this inclined discharge section to lift the sludge out of the liquid and hence permit additional quantities of liquid to drain by gravity therefrom back into the tank section prior to the filter media and sludge layer being discharged through the discharge opening. However, it has been observed that the sludge layer exiting the apparatus still contains an undesirably high quantity of moisture so that the sludge as deposited into an external receptacle is both wet and heavy. Since this sludge must subsequently be disposed of, either through further processing steps such as drying or incineration, or buried in authorized landfills, the further handling of such wet sludge is complex and/or expensive, with such handling being further complicated by the amount of moisture contained in the sludge since this hence requires either further external drying and treatment or significantly increases the cost of landfill disposal since such costs are normally determined based on volume and weight.
In one prior attempt to remove additional moisture from the sludge prior to discharge from the filtration unit, a suction or vacuum box was positioned within the discharge section directly over the sludge layer as the latter was moved up the inclined bottom wall of the discharge section. This suction box was connected in communication with an exteriorly-located suction unit, such as a motor-blower unit, and the latter in turn merely discharged the air externally of the unit. This suction box, however, was believed to be relatively ineffective, and received little if any commercial acceptance, because it in effect only caused additional air movement within the interior of the discharge section by drawing air from the interior of the unit along the surface of the sludge layer and thence into the suction box. The air had only minimal contact with the sludge layer, namely only along the upper surface thereof, and hence was ineffective in significantly reducing the moisture content of the sludge layer.
Accordingly, it is an object of this invention to provide an improved separating apparatus of the aforesaid type, which apparatus has a drying arrangement associated with the discharge section thereof so as to permit significant additional drying of the sludge layer prior to discharge of the sludge from the apparatus, thereby resulting in the discharged sludge having a significantly increased level of dryness.
More specifically, in the improved separation apparatus of this invention, which apparatus preferably comprises a coolant filtration unit which separates solids from liquid coolant, a vacuum-type dryer is preferably associated with the discharge section of the apparatus to permit passage of warm air transversely through the filter media and the sludge layer deposited thereon as said filter media and sludge layer are moved upwardly through the discharge section after leaving the tank section but prior to reaching the discharge opening. This vacuum-type dryer, by passing air transversely through the sludge layer, hence effects loosening of the material defining the sludge layer and intimate contact with the warm, dry air as it passes therethrough, whereby moisture from the sludge layer is picked up by the air and delivered to an exterior suction tank whereby the moisture can then be condensed and the air recirculated for further passage through the sludge layer. This dryer hence preferably constitutes a substantially closed-loop system so as to at least minimize any possibility of undesired contaminants being exteriorly discharged.
In the improved apparatus of this invention, particularly in the preferred embodiment, the housing of the apparatus includes a main section which defines a tank in which a bath of dirty coolant is contained, and a discharge section which includes a housing structure having a bottom guide wall which inclines upwardly as it projects outwardly away from the main tank section. The discharge section at its upper outer end terminates in a discharge opening for permitting external discharge of the sludge into an exterior receptacle. A suitable device such as an endless drag conveyor moves longitudinally along an intermediate bottom wall of the main tank section and then upwardly along the inclined bottom wall associated with the discharge section until reaching the discharge opening, at which location the drag conveyor is bent back over suitable supportive-type guides or sprockets so as to be resupplied back to the remote end of the tank section. A disposable paper filter media is preferably disposed directly under and moves with the lower reach of the drag conveyor as it moves along the bottom partition and the inclined bottom wall. The heavy solid contaminants in the dirty coolant contained within the tank section settle downwardly and collect on the paper filter media between the flights of the drag conveyor to create a layer of sludge-like material. At the same time, suction is preferably applied to a compartment defined below the bottom partition, the latter preferably being perforated, whereby coolant in the tank section is sucked downwardly through the sludge layer and the paper media, thus causing additional filtering of solids from the coolant, whereupon clean coolant passes into the suction chamber and is suitably removed therefrom for reuse. As the drag conveyor and filter media are slowly moved throughout the length of the tank section, the sludge layer builds up thereon. Upon reaching the discharge end of the tank section, then the drag conveyor and filter media carry the sludge layer upwardly along the inclined bottom wall of the discharge section, causing the sludge layer to be lifted upwardly out of the liquid bath. This permits some gravity-urged drainage of liquid in the sludge layer back into the bath. After leaving the bath and moving upwardly a selected distance along the inclined bottom wall, the sludge layer then moves slowly between cooperating portions of a dryer which is associated with the discharge section. The dryer preferably includes a closed pressure chamber which underlies the inclined bottom wall, the latter being perforated for communication with the pressure chamber, so that pressurized warm and relatively dry air can be discharged upwardly through the bottom wall and thence upwardly through the filter media and the sludge layer to effect removal of moisture therefrom. The dryer also includes a suction chamber positioned substantially coextensively with the pressure chamber but on the other side of the sludge layer so as to draw therein the moist air which passes upwardly through the sludge layer. This moist air from the pressure chamber is recirculated back to a motor-blower unit due to suction created by the blower. The moisture in the air is allowed to condense in a collection chamber associated with the motor-blower unit for resupply to the bath. The motor-blower unit effects repressurization of the air and causes the air to be resupplied to the pressure chamber. The heat generated by the motor-blower unit is effective in warming the air as resupplied to the pressure chamber.
Other objects and purposes of the invention will be apparent to persons familiar with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings.